Use of a PVDF pyroelectric sensor for beam mapping and profiling of a mid-infrared diode laser

A four-quadrant PVDF position sensor, originally designed for the alignment of mid-IR laser diodes beams, was also used for mapping and profiling the beam of a diode laser emitting few mu W at 5.8 mu m, by masking one quadran t with a 1 mm diameter pinhole or a 100 mu m width slit. This diagnostic sy stem was used to optimize the laser collimating optics, determining a signi ficant improvement in the spatial quality of the output beam, evaluated by means of the M-2 propagation factor. Since the laser diode modulation wavef orm required to optimize the pyroelectric detector responsivity is a fixed frequency square wave, quite different from that used in the normal spectro scopic application of the IR diodes, care was taken to have the same single -mode emission in the wavelength range of interest. The system was intended as a diagnostic and optimization tool for spectroscopic systems applied to environmental monitoring, but it may be used as a low cost device for the characterization of low power laser beams. (C) 2000 American Institute of P hysics. [S0034-6748(00)04404-X].